Pneumatically operated tool



April 21, 1964 C. A. SORENSEN ETAL PNEUMATICALLY OPERATED Filed June 26, 1961 Hill TOOL

CLARE/v05 A. SORE/VSEN 'VV/LLIAM WORKMA/V 1/9.

INVENTORS BYWLU-W ATTORNEY United States Patent 3,129,642 PNEUll/IATICALLY OPERATEB T891 Clarence A. Sorensen. Fruitport, and William Workman, Jr., Muskegon, Mich, assignors to Gardner- Denver Company, a corparation of Delaware Filed June 26, 1961, Ser. No. 119,395 2 Claims. (Cl. 91-121) The present invention broadly pertains to pneumatically operated tools adapted to drive working implements for drilling, hole tapping, screw driving, nut setting, and allied operations.

Tools of the aforedescribed character which are intended for mass production applications are commonly designed for manual operation. To increase operator efficiency in using such hand tools for highly repetitious operations, such as setting threaded fasteners, the tool may be resiliently suspended over a work area to enable an operator to grip the body of the tool, to apply the tool to the fastener, and thereafter to release the tool for automatic retraction to an initial suspended position. This invention contemplates a tool particularly well suited for the above described mode of operation in that the air motor of the tool may be controlled by an exhaust choke valve which energizes the motor when the tool is applied to the work and automatically deenergizes the motor when the tool is withdrawn from the work. In prior art tools of the type under consideration, the exhaust choke valve is usually disposed at or near the forward end of the tool, i.e. the end of the tool nearest the work and the work surface. In many conventional constructions, the movable element of the exhaust choke valve is directly connected to the shank of a working implement; and, the movable valve element is opened, thereby energizing the motor, in response to advancement of the tool body relative to the working implement.

Since the exhaust choke valve of a conventional tool is located at the forward end of the tool, the usual practice is to vent motor exhaust air from the front portion of the tool housing. This exhausting system typically comprises a passage for directing the exhaust air forwardly along the working implement or through exhaust ports in the nose of the tool. In either case, the exhaust air strikes the work area with considerable force. It has been observed that this force is suflicient to propel work pieces and particles, such as the loose screw shown in FIG. 1, for a considerable distance from the work area. Thus it will be apparent that this conventional method of tool exhausting creates a hazardous working condition for the tool operator and others in the Vicinity.

In accordance with conventional practice, a suitable lubricant is entrained in the motive air supplied to the aforedescribed type of tools to lubricate moving parts; and, a great portion of this lubricant is usually exhausted from the tool. If a tool is constructed to exhaust from its forward end, i.e. toward the work, the tool would be totally unsuited for applications requiring that the work be maintained substantially clean and oil free. One such application might involve setting screws into a panel carrying electrical terminals exposed to tool exhaust.

Accordingly, a broad object of the present invention is the provision of a pneumatically operated tool of the type under consideration which will solve the various problems above set forth by providing rearward exhausting of motive air.

Another object is to provide a tool of the aforesaid type which is structurally and operationally suited to include a rearwardly vented exhaust system having a relatively large mufiling element disposed at the rear end of the tool body. A related object is the provision of an exhaust system having an expansion chamber extending ice along and around a substantial portion of the tool body, the expansion chamber being cooperable with the above mentioned muffling element to provide extremely quiet tool operation.

Yet another object is to provide an improved exhaust choke valve for tools of the aforesaid character requiring a small axially applied force to operate the same, thereby reducing operator fatigue and potentially damaging compressive forces upon lightly constructed work pieces.

For the attainment of the above stated objects and other more detailed objects and advantages which will hereinafter appear, the invention generally contemplates an improved tool having a body comprised of a pair of telescoping cylinders, a pneumatic motor housed in the inner cylinder, an exhaust choke valve operable to control the motor in response to telescoping movement of the cylinders, and an annular expansion chamber defined by the cylinders for expanding exhaust air and communicating the same from the choke valve to the rear end of the tool through a mufliing element and then to atmosphere.

These and other objects and advantages Will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawings in which:

FIG. 1 is a longitudinal sectional view of a tool constructed in accordance with the present invention;

FIG. 2 is an enlarged fragmentary view of a valve shown in FIG. 1; and,

FIG. 3 is a transverse sectional view taken along lines 3-3 of FIG. 1.

In the drawing, the present invention is embodied in a hand tool designated in its entirety by numeral 10. The exemplary tool is adapted to be powered by pressure fluid, such as compressed air; however, it is not intended that the invention be limited thereto. As will hereinafter appear, the exemplary tool 10 comprises a portable device for performing highly repetitive screw driving operations; however, the basic tool structure is readily adaptable for use with other working implements to perform allied operations.

Referring to FIG. 1, the tool 10 essentially comprises a plural part housing, generally designated by numeral 12; an air motor 14 disposed in the housing 12 for rotating a screw driving implement 16 through speed reduction gearing 18 and an implement spindle 20.

As seen in FIGS. 1 and 3, a pair of telescoping cylinders 22 and 24, together with forward extensions thereof,

provide inner and outer members of the housing 12 which respectively extend substantially the full length of the tool 10. The outer housing member comprises cylinder 22 and a forwardly extending sleeve 26; and, the inner housing member comprises cylinder 24, a back head 28 and front head 30 respectively received in opposite threaded ends of cylinder 24, and a nose piece 32 threadably attached to the forward end of front head 30. The inner and outer cylinders of the housing 12 are axially movable with respect to one another for a purpose to be described.

A rotary air motor 14 of the sliding vane type is disposed within the inner cylinder 24 near the rear end of the latter. Since the structure and operation of motor 14 are well known, the motor will not be herein described in detail. The motor 14 includes an eccentrically bored cylinder 34 closed at opposite ends by end plates 36 and 38. The rear end plate 36 abuts the back head 28 and the forward end plate abuts a rear gear plate 40. A motor spindle 42 is rotatably supported with respect to motor end plates 36 and 38 by a pair of ball bearing elements 44 and 46. A pinion gear 48, integrally formed on spindle 42, extends forwardly through the rear gear plate 40 into intermeshing, driving engagement with gears 50. The gears 50 are rotatably journalled upon pins 52 which have their opposite ends supported in the rear gear plate 40 and a forward gear plate 54. The gears 58 are provided with teeth formed on different diameters at opposite ends; and, the gear teeth coact with pinions 48 and 56 to effect a reduction in the speed of rotation of the implement spindle 28 with respect to the motor spindle 42. It will be understood that, if desired, further steps of speed reduction may be provided by additional reduction gearing of the same or equivalent construction.

The rear end of implement spindle 20 is rotatably journalled by a ball bearing 58 seated in a forwardly opening cylindrical recess 68 in the forward gear plate 54. The forward enlarged end 21 of the implement spindle is rotatably journalled by a conventional needle bearing 62 which is seated in a rearwardly opening recess in the nose piece 32'. The central body portion of the implement spindle extends coaxially through a stepped bore 64 in the front head 30. A rearwardly opening enlargement 66 of bore 64 and recess 60 define an exhaust chamber 68 intended for a purpose to be described. An internal flange 70 in bore 64 is provided with an annular groove opening toward implement spindle 20; and, the groove holds a resilient sealing body or ring 72 in air tight sealing engagement about the implement spindle. The enlarged forward end 21 of implement spindle 20 is suitably constructed for receiving and detachably retaining a screw driving bit 16 or similar working implements.

Motive air for motor 14 is communicated from a compressed air source, not shown, to the back head 28 of tool by a conduit 74 which is detachably connected to an air supply chamber 76 by a threaded fitting 78. The motor 14 is in open communication with the air supply chamber 76 by means of an air conducting passage 88 extending through back head 28 and motor end plate 36 and opening to the motor inlet 82. After motive air is partially expanded in motor 14 to drive the latter, the air is exhausted through the motor exhaust port 84, through a passage 86 in the motor end plate 38, through the aforedescribecl reduction gearing 18, and along implement spindle 28 into the aforementioned exhaust chamber 68. The O ring 72 prevents leakage from exhaust chamber 68 in a forward direction along the implement spindle 20.

In the illustrative embodiment of this invention, an annular valve chamber 88 is generally defined between front head 30 and sleeve 26; and, this valve chamber is in communication with exhaust chamber 68 by means of diagonal air passages 90. An 0 ring 92' is disposed in an annular groove about front head 30 to provide an airtight seal at the forward end of valve chamber 88. The rear end of valve chamber 88 is closed by an exhaust choke valve, designated generally by numeral 94, comprising mating, frustro-conical valve seats 96 and 98 which are respectively formed at the forward end of cylinder 24 and the rear end of sleeve 26. As best seen in FIG. 2, an 0 ring 1% is carried in an annular groove 182 relieved in valve seat 96 and provides an air-tight seal with valve seat 98 when the exhaust choke valve 94 is in the closed condition, as shown in FIG. 1. As will be hereinafter described, the exhaust choke valve 94 is operable to the open position shown in FIG. 2, thereby exhausting the valve chamber 88 to atmosphere by means of an annular expansion chamber 104 defined by cylinders 22 and 24. The annular expansion chamber 104 extends along a substantial portion of the length of tool 10 and opens through a muflling element 106 to the extreme rear end of the tool. The muffiing element 186 is fabricated of any material having suitable sound mufiling characteristics and is preferably annular in form in order to close the open rear end of the annular expansion chamber 184 and to receive centrally a reduced cylindrical portion 27 of back head 28. The muflling element 186 and a perforated backing disc 198 are held in assembled relationship with respect to back head 28 by means of washer 118 which coacts with the fitting 78.

The exhaust choke valve 94 is operated from the closed condition, shown in FIG. 1, to the open or exhausting condition, shown in FIG. 2, in response to relative axial movement of the tool parts which carry the reversely tapered valve seats 96 and 98. The outer cylinder 22, including its sleeve extension 26, is slidably journalled at its opposite ends by the mufiler backing disc 108 and by a cylindrical portion 112 of nose piece 32. With the screw driver bit 16 applied to screw 114, as shown in FIG. 1, forward axial movement of cylinder 22 and sleeve 26 will cause valve seat 98 to disengage the valve seat 96 and to move forwardly to a position substantially as shown in FIG. 2. This forward movement will compress a coiled return spring 116 seated between an annular shoulder 118 on sleeve 26 and an annular rear surface 120 of nose piece 32'. When the screw driver bit 16 is lifted from the screw 114, the spring 116 will bias the nose piece 32, the front head 30 and inner cylinder 24 urging the valve seat 96 into reengagement with the valve seat 98 and the O ring 100.

One practical application of the illustrative screw setting tool 10 involves attaching a metallic bus bar strip 122 to a terminal insulating block 124. In the exemplary application, the terminal block is disposed on a suitable work surface, not shown; and, the tool 10 is resiliently suspended immediately above the work surface to permit the operator to grasp the tool housing 12, to apply the screw driving bit 16 for running down the screw, and, thereafter, to release the tool for retraction to a suspended position. In carrying out the above described sequence of operations, the bit driving motor 14 is started by applying the screw driving bit to a screw, as shown in FIG. 1, and urging cylinder 22 and sleeve 26 forwardly or downwardly against the bias of spring 116 to open the exhaust choke valve 94. With the exhaust choke valve 94 actuated to the open condition, motive air will be permitted to flow from the air supply chamber 76 through motor 14 and then forwardly to the exhaust chamber 68. From the exhaust chamber 68 the exhausted air from motor 14 enters valve chamber 88 by means of passages and then flows between the now opened valve seats 96 and 98 to the annular expansion chamber 104 and rearwardly through mufiling element 106 to atmosphere.

As previously stated, the tool 10 is actuated by exerting forward axial force on the outer portion of tool housting 12 after the screw driver bit 16 is applied to screw 114. This forward movement compresses the spring 116; and, when the operator releases the bit '16 from the screw 1114, the spring will return the elements of the tool housing to the position shown in FIG. 1, thereby closing the exhaust choke valve 94 and stopping the rotation of the motor and the bit 16.

From the foregoing, it will be apparent that a pneumatically operated tool constructed and arranged in a cordance with the teachings of the present invention is particularly well suited for rapidly performing repetitious assembling operations. Furthermore, in the performance of such operations, exhaust air is directed from. the rear of the tool in a direction away from the work area and the operator. The advantages of this operational feature of the present invention are particularly apparent when contrasted with the dangers and difiiculties encountered in using conventional air tools in which motor exhaust is emitted from the tool in the direction of the work area, the work piece and the operator. In such conventional tool constructions, exhaust air may strike and propel small parts, such as the screw 128 or other particles, with sutficient force to cause injury to the operator or others nearby. I

Another objection to the exhaust systems of conventional tools is that oil laden exhaust air is blown on and over the work and possibly onto the operators body and clothing. The work piece shown in FIG. 1 which comprises an insulating terminal block 12 4 with exposed terminals 126 extending therefrom would undoubtedly require subsequent cleaning to remove the oil film deposited thereon by tool exhaust. Moreover, this additional operation required to produce clean part surfaces would increase the manufacturing costs of such an article. Furthermore, oil film deposited on the work and on the operators hands would make part handling more diflicult and hazardous and would create an. unpleasant and perhaps unhealthy working condition. The present invention, with rear exhausting, eliminates these difliculties encountered in usage of conventional tools of the type under consideration.

In carrying out another important aspect of the present invention, a large annular chamber 104 is defined on the downstream side of the choke valve 94 to receive and to expand further the partially expanded motive air exhausted from motor 14. The additional expanding action occurring chamber 104 reduces final exhaust air pressure to a lower value than that produced with conventional tools; therefore, the exhaust air impacts the remotely spaced muifler element 106 and its backing disc 108 at a lower velocity. This feature of the invention greatly reduces the pitch and intensity of the noise typically accompanying operation of tools of the rotary vane type. In addition to expanding exhaust air for the purpose set forth, the relatively lengthy expansion chamber 104 inherently acts as a muffling or sound dampening device.

An ancillary advantage aiforded by the rearwardly directed exhaust system of this invention is that this tool construction is adapted to incorporate an internally received mufliing element which is dimensionally large enough to produce eifective sound reduction. This is in co-ntradistinction to conventional [forward exhausting systems in which the space available at the front end of the tool is usually suflicient for mounting only relatively smaller and substantially less eifective mufliers. Although a single mufiling element 106 is provided in the exemplary tool, it will be obvious from the present disclosure that the back head could be modified to receive additional elements or a larger single element if greater mufliing action were required. From the foregoing, it will be appreciated that the pneumatic tool structure hereindisclosed provides a novel rearward exhausting systern productive of improved sound reduction by means of (l) exhaust expansion, (2) sound dampening, and (3) advantageous muffler positioning with respect to other parts of the tool.

Another important feature of this invention resides in the improved construction and operation of the exhaust choke valve 94. It will be noted that, in the present constnuction, the operator is not required to overcome a resistance to movement created by exhaust air pressure. When the valve 94 is closed, as shown in FIG. 1, the air pressure in the valve chamber 88 does not resist valve operating movement of the sleeve 26'. The 'only resistance to valve opening is produced by the resistance to compression exhibited by the coiled return spring 116; therefore, the exhaust choke valve may be operated by a force just sufiicient to compress spring 116. Thus, valve 94 provides a mode of tool operation which reduces operator fatigue to a minimum and permits the operator to apply only a slight compressive force to work pieces which are lightly constructed. Moreover, the valve seats 6 96 and 98 may be separated with a smooth action to provide closely controlled motor throttling and efficient tool usage in applications involving small parts.

While the improved exhausting system has been shown and described as having particular utility when. employed with a screw driving tool powered by a sliding vane air motor, it will be appreciated that the invention broadly contemplates a rear exhaust system for a tool having a pneumatic motor controlled by an exhaust choke valve. Moreover, it will be understood that the above description and accompanying drawing comprehend only a general and preferred embodiment of the invention and that various changes: in construction, proportion, and arrangement of parts may be made without departing from the spirit of the invention as set forth in the appended lclaims.

Having fully described the invention, what is claimed as new and useful 1. In a power tool: inner and outer telescoping tubular members respectively extending substantially the full length of said tool; pressure fluid motor means disposed Within said inner member; axially spaced motor exhaust receiving chambers defined by and between said members; and, an exhaust choke valve disposed between said chambers to control the flow of exhaust therebetween and operable for starting and stopping said motor means in response to telescoping movement of said members.

2. In a power tool: inner and outer telescoping tubular members respectively extending substantially the full length of said tool; pressure fluid motor means disposed within said inner member for driving an implement disposed within a forward portion of said inner member; axially spaced motor exhaust receiving chambers defined by and between said members; an exhaust choke valve disposed between said chambers to control the flow of exhaust therebetween and operable for starting and stopping said motor means in response to telescoping movement of said members; and, one of said chambers extending along and about a rear portion of said inner member for conununicating exhaust from another of said chambers to atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS 550,324 King Nov. 26, 1895 1,652,374 Price Dec. -13, 1927 2,423,957 Amtsberg July 15, 1947 2,484,364 Whitledge Oct. 11, 1949 2,552,840 Burke et al. May 15, 1951 2,570,009 Schmid Oct. 2, 1951 2,580,607 Schmid Jan. 1, 1952 2,643,731 Schm'id June 30, 1953 2,763,472 Fontaine Sept. 18, 1956 2,780,966 Frost et a1. Feb. 12, 1957 2,905,149 Swanson Sept. 22, 1959 2,966,138 Quackenbush Dec. 27, 1960 3,049,098 Innue Aug. 14, 1962 FOREIGN PATENTS 847,396 Great Britain Sept. 7, 1960 

1. IN A POWER TOOL; INNER AND OUTER TELESCOPING TUBULAR MEMBERS RESPECTIVELY EXTENDING SUBSTANTIALLY THE FULL LENGTH OF SAID TOOL; PRESSURE FLUID MOTOR MEANS DISPOSED WITHIN SAID INNER MEMBERS; AXIALLY SPACED MOTOR EXHAUSTED RECEIVING CHAMBERS DEFINED BY AND BETWEEN SAID MEMBERS; AND, AN EXHAUST CHOKE VALVE DISPOSED BETWEEN SAID CHAMBERS TO CONTROL THE FLOW OF EXHAUST THEREBETWEEN AND OPERABLE FOR STARTING AND STOPPING SAID MOTOR MEANS IN RESPONSE TO TELESCOPING MOVEMENT OF SAID MEMBERS. 